Locating devices are used to detect, for example wires, pipes, metal bars, wooden beams or other objects embedded in walls, ceilings or floors. Inductive devices, among other things, are used, i.e., devices that generate a magnetic field which is disturbed by the metallic objects enclosed in a medium. In addition to the inductive devices, capacitive devices, line voltage detectors and high-frequency detectors are also used.
Most of these devices must be calibrated when powered on or at regular intervals. For this purpose, an internal electronic adjustment is usually carried out which must take place in a measurement environment in which no objects to be located may be present close to the measuring device sensor. For example, metal locating devices must be calibrated at a great distance from any metal present in the vicinity. To do this, for example, the device must be held in the air away from the wall to be examined.
The enormous dynamics of the sensors used, which occur despite calibration of the measuring device, present a problem that arises, in particular, with inductive and capacitive locating devices. In addition to the depth of the objects to be measured in the surrounding medium, the extremely wide range of dynamics of the measuring signal of sensors of this type, also results, for example, from the type of metal detected. For example, a copper cable embedded deep in a wall generates a sensor signal that is several times weaker than, for example, an iron pipe embedded at a depth of 2 cm. Due to the limited display area of the locating devices according to the related art, dynamics of this type are difficult to display.
To date, two methods are known from the related art which make it possible to solve the problem associated with the enormous dynamic range.
It is possible to design the measuring device display so that the entire dynamic range is shown. This is achievable, for example, by a logarithmic scale for the display variable correlated with the measuring signal. However, the disadvantage of a display of this type is that weak or even very strong objects appear at the beginning and end of the dynamic range of the displayed scale and are therefore very difficult to locate, since the changes shown in the measuring device display are too small.
A method for designing the measuring device so that it automatically determines the necessary sensitivity is also known from the related art. The measuring device is operated so that it is first set to maximum sensitivity and, when a strong measuring signal is detected, the sensitivity is reset so that the representation of the output variable of the measuring device correlated with the measuring signal always remains in the center of the viewing area available in the device display. To achieve this, however, the measuring device must be passed multiple times over the object to be measured to make the necessary sensitivity settings. In addition, the user loses the information about the absolute signal strength.